Wednesday, May 4, 2011

World Population to reach 10 billion by 2100 if Fertility in all Countries Converges to Replacement Level

The current world population of close to 7 billion is projected to reach 10.1 billion in the next ninety years, reaching 9.3 billion by the middle of this century, according to the medium variant of the 2010 Revision of World Population Prospects, the official United Nations population projections prepared by the Population Division of the Department of Economic and Social Affairs, which is being launched today. Much of this increase is projected to come from the high-fertility countries, which comprise 39 countries in Africa, nine in Asia, six in Oceania and four in Latin America.

Small variations in fertility can produce major differences in the size of populations over the long run. The high projection variant, whose fertility is just half a child above that in the medium variant, produces a world population of 10.6 billion in 2050 and 15.8 billion in 2100. The low variant, whose fertility remains half a child below that of the medium, produces a population that reaches 8.1 billion in 2050 and declines towards the second half of this century to reach 6.2 billion in 2100. For long-term trends the medium variant is taken as reference.

The medium-variant projection for 2050 is more certain than for 2100 because people who will be 40 years and older in 2050 are already born. According to the medium variant, it will take 13 years to add the eighth billion, 18 years to add the ninth billion and
40 years to reach the tenth billion. According to the high variant, an additional billion would be added every 10 or 11 years for the rest of this century.
Current fertility levels vary markedly among countries. Today, 42 per cent of the world’s population lives in low-fertility countries, that is, countries where women are not having enough children to ensure that, on average, each woman is replaced by a daughter who survives to the age of procreation. Another 40 per cent lives in intermediate-fertility countries where each woman is having, on average, between 1 and 1.5 daughters, and the remaining 18 per cent lives in high-fertility countries where the average woman has more than 1.5 daughters (see map).

High-fertility countries are mostly concentrated in Africa (39 out of the 55 countries in the continent have high fertility), but there are also nine in Asia, six in Oceania and four in Latin America. Low-fertility countries include all countries in Europe except Iceland and Ireland, 19 out of the 51 in Asia, 14 out of the 39 in the Americas, two in Africa
(Mauritius and Tunisia) and one in Oceania (Australia).